Upload a MP3 file and get a AAC back. No signup, no watermark, no limit on how many.
MP3 is the format that made portable music work, and thirty years on it is still the one every device, car stereo, DAW and browser will open without being asked twice.
Where you run into it: Downloads, podcast feeds, old music libraries, anything a client sends you and expects you to just play.
What it costs you: It throws audio away to get small, and at 320 kbps almost nobody can hear what went. What matters is that the discarded part never comes back.
AAC is MP3's designated successor and wins at low bitrates by a clear margin. A bare .aac file is the raw ADTS stream rather than the .m4a container most software expects.
Where you run into it: YouTube and streaming audio tracks, broadcast, anything that came out of a device rather than a music shop.
What it costs you: The naked .aac extension confuses a surprising amount of software, which is the usual reason people convert it.
This writes a bare AAC stream — the audio frames on their own, with no container around them. The MP3 is decoded and encoded again, so it is a second generation, and at 192 kbps or Best quality the result holds what the source still had. The thing to understand before you download it is that a naked .aac is a stream, not a document: it carries no duration, no tags, no cover art and no seek table, which is exactly why some players show it as an unknown length and refuse to scrub.
Most people who ask for AAC actually want M4A. The two hold the same audio — .m4a is an MP4 container wrapped around exactly these AAC frames — but the container is what gives you a readable length, working seek, tags, artwork and an import that iTunes and Apple Music will accept. If you are converting for a phone, a music library or a car, use MP3 to M4A instead. A bare .aac is the right answer only when something downstream specifically wants an ADTS stream, which in practice means broadcast and streaming tooling.
Yes, entirely, and there is no cap on how many files you convert. No account, no watermark, no trial.
A little, as with any second pass between lossy codecs. AAC is the more efficient of the two, so 192 kbps or Best quality preserves what the MP3 was still carrying. The bitrate is the only real decision here; going below the source's own rate is what makes the loss audible.
Similar, and marginally smaller than the MP3 at matched quality, partly because AAC is more efficient and partly because a raw stream has no container or tag overhead at all. That missing overhead is also the missing duration and artwork.
Yes — AAC is one of the formats this converter writes, so the reverse page exists at /aac-to-mp3/. Both formats are lossy, so every leg re-encodes: going out and coming back costs two more generations, and the damage accumulates.
The file is uploaded to do the conversion — nothing here runs in your browser — and both your upload and the converted result are deleted the moment the file is sent back. Nothing is stored and nothing is logged beyond the request itself.